Many of us here in the TALON (TX, AR, LA, OK, NM) area sign up for races in the mountains at altitudes significantly higher than where we train. Indeed, there were over 75 TALON athletes (including myself) who ran the Leadville 100 last year, which starts at 10,200 feet. I imagine even more of us are signed up this year. So it seems timely to discuss altitude illness.

Leadville 100 Course Inbound: Heading up to the top of Hope Pass (elevation – 12,620 feet), turning around and looking South. (Photo: David Hanenburg)

Most of us lowlanders have been told that we should plan to arrive a few days, or even a few weeks early to a mountain race. We’ll have a horrible race otherwise. We’ll probably have to drop. When I signed up for Leadville in 2010, people told me I needed to get to town at least three weeks before the race. “Five weeks would be better.” Other people told me I could show up the day before the race and I’d be fine.

“Just don’t arrive three days early!” one fellow warned me.

“You always feel the worst on the third day.”

“Are you going to sleep in an altitude tent?”

“Have you heard about those oxygen deprivation acclimatization masks?”

“Make sure you drink lots and lots of water!”

The questions and conflicting information were overwhelming — even though I’d taught about altitude sickness and acclimatization for 10 years for Wilderness Medicine Institute and worked as a field instructor in the mountains for the National Outdoor Leadership School. I wanted something written specifically for a lowland ultrarunner. I hope this article can be that for you.

First of all, there’s just as much oxygen in Leadville at 10,200 feet as there is here in San Antonio and wherever you live – 21%. It’s just that the oxygen around High Mountain Pies in Leadville is more spread out than it is down here. So there’s less pressure from the oxygen surrounding you while you’re eating your pizza up there. In fact, Leadville’s oxygen pressure is about a third less than the pressure at sea level. And that decreased pressure makes it more difficult for the oxygen you breath in to load onto your red blood cells. It also makes it more difficult for the oxygen to unload once it reaches your cells. (i.e. Your legs feel like lead because they’re not getting as much oxygen as they’re used to.)

The hangover-like symptoms of mild altitude sickness result from this altered diffusion and delivery of oxygen. Headache, nausea, fatigue, lack of appetite, possible vomiting (Sound like you last hangover?), trouble sleeping, and shortness of breath are common symptoms. The headache is key though. The actual definition of altitude sickness is “headache with one or more of the following symptoms.” People rate the headache anywhere from a 1 to a 10 on a scale of 1-10. I usually wake up my second day in town with an 11.

The good news is that if you give your body time, it can adapt to the decreased oxygen pressure. It will acclimatize. In fact, the process starts as soon as you step off the plane in Denver. Your heart rate increases to circulate oxygen more efficiently. And your respiratory rate and the depth of your breathing also increase, so you can take in as much oxygen as possible. The pressure in your pulmonary arteries (those lung arteries) also increases, which allows for more oxygen to load onto the red blood cells. (The increased pressure forces the capillaries around your alveoli to open, which allows for greater gas exchange.)

In a few hours (maybe by the time you’ve stopped for lunch on the drive from Denver to Leadville), more adaptations have started. You’ll probably need to use the bathroom because you’ll start to urinate more. You’ve made yourself a bit alkaline with all that rapid, deep breathing, so the kidneys act to balance your pH levels by spilling bicarbonate in your urine. (This is one of the reasons you’re more likely to get dehydrated at altitude: Increased peeing and increased breathing. And this is why you may need to drink a bit more at altitude than you do when you’re at home. Hydration doesn’t help you acclimatize, but it does prevent you from becoming dehydrated.) A few hours after your flight, your kidneys will also send a signal to increase red blood cell production, and to produce a chemical that will allow oxygen to unload from the red blood cells more easily. You’ll also grow more capillaries and more mitochondria (those “power houses of the cells” that you learned about in 7th grade). And finally, you’ll produce more myoglobin, which stores oxygen in your muscles and provides it when needed. The body is amazing.

The problem, as far as our race plans are concerned, is that this all takes a while. In fact, it takes about six weeks to get 95% acclimatized and 10 days for 80% acclimatization. But most of us have work and family responsibilities that won’t allow us to show up 10 days before a race – much less 42 days. Understand that you are unlikely to be dealing with altitude sickness after three days. The symptoms usually present within 12-24 hours, and then take a day or two to resolve. You still won’t perform like you would at sea level, but you won’t feel sick. You’re definitely rolling the dice if you plan to arrive the night before a mountain race. I’ve known people who have done it successfully, and I’ve known people who have had to drop because they got so sick all they could do was curl up in a ball and vomit until they were carted off to a lower altitude. Your odds are definitely better with a 50-mile race than a 100-mile one if you have to arrive the night before. I think a good guideline is: Show up as early as you can for a race that’s important to you.

You can take pain medications for your altitude headache. I always bring a nice supply of ibuprofen for the days before Leadville. Avoid sedatives to help you sleep though, because they’ll decrease your respiratory rate and inhibit acclimatization. Diamox (acetazolamide, a sulfa drug) will also reduce the symptoms of altitude sickness– though there are no studies testing its use during ultramarathons. It promotes the spilling of bicarbonate in your urine, which allows you to keep breathing at an increased rate as described earlier. This is particularly useful when your respiratory rate slows at night while you’re sleeping. Remember though, that you have to stay on top of your hydration when you’re using Diamox because you’ll be urinating more. It can also cause your lips, fingers, and toes to tingle and it can make Coke taste horrible (which is definitely a bummer late in a race.)

The only cure for mild altitude sickness, however, is descent. Get down. Go lower. 1000-2000 feet usually does the trick. Last year I drove down to Buena Vista from Leadville for a day for a little headache relief and some good coffee.

It’s important to know that severe altitude illness is deadly. Fluid can accumulate in your lungs with High Altitude Pulmonary Edema (HAPE) or your brain, High Altitude Cerebral Edema (HACE). Either of these conditions can occur in Leadville or anywhere above 8000 feet. Being short of breath while you are sitting and resting for a while is an early sign of HAPE. And not being able to walk heel to toe in a straight line is an initial sign of HACE. Let your crew know to watch for these things – in you and in each other. If someone seems more clumsy than usual, it’s a good time to ask him or her to perform the heel to toe walk. You must immediately descend 2000-4000 feet with HAPE or HACE and seek medical attention.

Using a hypoxic training mask will not prevent altitude illness. These masks definitely make it harder to breathe, but they do not simulate the decreased oxygen pressure of altitude. The pressure remains whatever it is where you’re running. And I haven’t seen any research that shows these masks cause an increase in red blood cell production or any other acclimatization effects. Certainly you may get used to running while struggling to breathe with one of these things strapped to your face, which might be good mental training during a race, but that’s not the topic here. (Besides, doesn’t running in 95-105 degrees and 90% humidity make us mentally tough enough already?)

Hypoxic sleeping tents can simulate decreased oxygen pressure and do produce acclimation effects, but they’re pretty pricey at “$2,500 to more than $5000” and require a 16-hour a day commitment. (http://running.competitor.com/2012/02/shoes-and-gear/should-you-invest-in-an-altitude-tent_46687)

There is also some evidence that frequent exposure to altitude facilitates the acclimatization process (Muza, Stephen, and Beth A. Beidleman, and Charles S. Fulco. “Altitude Preexposure Recommendations for Inducing Acclimatization.” High Altitude Medicine & Biology 11, 2. (2010): 87-92. http://www.liebertpub.com/overview/high-altitude-medicine-and-biology/65/. Web. March 2013.) Theoretically if you can travel to the mountains to train a number of times before your race, you will have an easier time acclimatizing. I definitely get less sick now when I travel to Leadville than I did when I first traveled there. But I still always get sick.

I hope you are able to escape to the mountains a lot this summer and I hope this guide helps some.

Please let me know what questions you have.

– Liza Howard

About the author

Liza Howard became addicted to ultra running belt buckles back in 2008 and now runs for New Balance and coaches fellow ultra runners. She also teaches for the Wilderness Medicine Institute and is a field instructor for the National Outdoor Leadership School. For more information on Liza, check out the About page where you can learn about her coaching, trail running camp, and daily life musings.

Great article, Lisa, thanks. I’m from Fort Worth and am signed up to run the Aspen Back Country trail marathon on June 29. Thankfully, I should have time to acclimatize (at least to 80%!) as this will come at the end of a 2 week vacation in Estes Park/Rocky Mountain National forest. Any tips on race pace at that elevation compared to normal low-land trail pace? I’ve run races with similar total climbing, just not at that altitude. Or is survival just the main goal for a first race at altitude?

Thanks Liza! Just in time for Angel Fire 50K next month. I have heard so much conflicting information over the years regarding altitude sickness and really didn’t know what was right and what wasn’t. Great information!

Thanks for the nice comments everybody.
Mark, I think your pacing strategy shouldn’t change from the usual “find a comfortable pace through the half-way point and then push if you can.” Mostly just be prepared for the possibility that your stomach may be less cooperative than usual.

Nice to hear your experience and expertise! I did leadville last year and am headed back this year. I was inundated with all kinds of conflicting advise last year and I had no idea what to expect. Your write up confirms what I learned through trial and error and makes me more confident that I was on the right track then and now.